1. Field of the Invention
The invention relates to catalyst components and systems for the polymerization of olefins, methods of preparing the same, and methods of polymerizing
1-olefins with the catalyst systems.
2. Description of Related Technology
Ziegler-Natta catalyst components for olefin polymerization having transition metal compounds deposited on carriers are well known. These catalysts are distinguishable from earlier, unsupported Ziegler-Natta catalysts in that they often have improved activity per unit weight of catalyst and/or lead to decreased amounts of active catalyst residues persisting in the polymer product.
Depositing transition metal compounds onto the surface of an inert particulate support material has the dual purpose of creating a catalyst component which efficiently utilizes the transition metal, thus eliminating the necessity for costly removal of catalyst residues from product polymer, and of producing a catalyst component which is uniform in particle size and shape. The morphology of the catalyst particle is replicated in the polymer particle during polymerization. Thus it is important for catalyst performance, particularly in gas-phase polymerization processes, that the catalyst be as uniform as possible in size and shape.
Many prior olefin polymerization catalysts utilized metal oxides such as silica or alumina as a support material for the deposition of transition metal compounds. The vast majority of these are suitable only for polymerization of ethylene or copolymerization of ethylene with other olefins. Very few have been intended for polymerization of higher olefins such as propylene.
A catalyst component for propylene polymerization in which a porous inorganic oxide material, such as silica, is treated with a dihydrocarbylmagnesium compound and then with a halogenating agent, a Lewis base compound, and titanium tetrachloride is described in Caunt, et al. U.S. Pat. No. 4,301,029 (Nov. 17, 1981). A similar catalyst component is described in Gavens, et al. U.S. Pat. No. 4,329,252 (May 11, 1982) in which the organomagnesium compound is a hydrocarbylmagnesium chloride (a Grignard reagent). These catalysts, however, are not high activity catalysts for the polymerization of propylene.
A class of olefin polymerization catalysts in which organomagnesium silylamide compounds are reacted with transition metal halides is described in Pullukat, et al. U.S. Pat. No. 4,499,198 (Feb. 12, 1985). One class of these compounds has the general structure ##STR1## where R and R' are hydrocarbyl groups and Y is an alkyl, aryl or a tri-substituted silane group.